Surveillance reports show few pandemic flu hot spots

May 14, 2010 (CIDRAP News) – Low levels of flu activity across the United States resemble a summer pattern, while globally only sporadic pandemic flu activity is occurring with the most active areas in parts of the Caribbean and Central America, according to updates today.

For the fourth week in a row no US states reported widespread activity, the Centers for Disease Control and Prevention (CDC) said today in its report for the week ending May 8. Hawaii was the only state reporting local flu activity. Half of the states and US territories reported sporadic influenza activity, with the other half reporting no activity.

Physician visits for flu-like illnesses stayed below the national baseline, and the CDC said lab-confirmed hospitalization rates have leveled out.

Deaths from pneumonia and flu continued to sink well below the seasonal baseline, and the CDC received no new reports of pediatric flu deaths.

Of 1,722 respiratory specimens tested during the latest surveillance week, only 1.5% were positive for influenza. All were influenza A, of which just over 65% were the pandemic H1N1 subtype. Subtyping was not performed for about 31% of the influenza A viruses. No influenza B viruses were detected, and one specimen tested positive for the seasonal A/H3N2 virus.

Internationally, flu activity was also low in temperate areas of the Northern and Southern Hemispheres, according to the World Health Organization (WHO), but sporadic in some tropical areas such as some Caribbean and Central American countries. Pandemic flu was geographically widespread in Jamaica and the Dominican Republic, though other respiratory viruses are cocirculating, as well.

Intense pandemic flu transmission recently reported in Cuba appears to have peaked in late April, the WHO said.

Regional pandemic flu spread was reported in other Central America and tropical areas of South America countries, though illnesses such as respiratory syncytial virus (RSV) and adenovirus are also circulating. The WHO added that Chile continues to report local increases of pandemic flu infections, along with other respiratory illnesses.

Active areas of pandemic flu transmission in Southeast Asia include Bangladesh, Malaysia, and Singapore, the WHO said. Earlier this week a Malaysian health ministry official reported clusters of flulike illnesses in Kuala Lumpur and five states and that 13 patients were being treated in intensive care units, according to a May 12 report from Bernama, a Malaysia-based news agency. The WHO said pandemic flu activity in the country has been elevated since the middle of April.

East Asian countries such as China and areas such as Hong Kong and Taipei continue to report low but persistent levels of influenza B transmission, according to the WHO.

In the Southern Hemisphere, which is entering its winter flu season, New Zealand health officials recently reported a rise in flulike illnesses, though levels were still below baseline, and Australian authorities reported relatively low levels of flu-like illnesses, some of which they attributed to RSV and other viruses.

Pandemic flu activity in African countries appears to be subsiding, with influenza B virus cocirculating in some areas such as Cameroon. Namibia's health ministry reported 80 suspected pandemic flu infections from 5 of the country's 13 regions, the South Africa based Southern Times reported today. Seven of the cases have been confirmed, and test results are pending on 73 other cases.

In European countries, pandemic flu and other respiratory infection activity remained sporadic, with influenza B persisting in many areas, especially the Russian Federation and Italy. However, on the global level the pandemic H1N1 virus still predominates, making up nearly 100% of flu viruses typed in Canada, Chile, and the United States and accounting for 84% of viruses subtyped overall.

Four more cases of oseltamivir-resistant pandemic H1N1 were reported to the WHO for the week ending May 12, raising the global total to 289. The CDC today reported no new cases of osteltamivir resistance in the United States.